Field of the Invention
The present invention relates to a display device, and more particularly, to a touch sensor integrated type display device capable of recognizing a user's touch operation.
Discussion of the Related Art
In recent years, various input devices, such as a keyboard, a mouse, a joystick, and a digitizer, have been used to allow users to interface with home appliances or information telecommunication devices. However, when the user makes use of these input devices, user's dissatisfaction increases because the user is required to learn how to use the input devices and the input devices occupy space. Therefore, a convenient and simple input device capable of reducing erroneous operations is required. In response to this demand, a touch sensor for enabling the user to input information by directly touching the screen with his or her hand or a pen was suggested.
The touch sensor has a simple configuration capable of reducing the erroneous operations. The user can also perform an input action without using a separate input device and can quickly and easily manipulate a display device through the contents displayed on the screen. Accordingly, the touch sensor has been applied to various display devices.
The touch sensor used in the display devices may be classified into an add-on type touch sensor and an on-cell type touch sensor. The add-on type touch sensor is configured such that a display device and a touch sensor are individually manufactured and then the touch sensor is attached to an upper substrate of the display device. The on-cell type touch sensor is configured such that components constituting a touch sensor are directly formed on the surface of an upper glass substrate of the display device.
There is a problem of an increase in a thickness of the display device because the add-on type touch sensor has a structure in which the touch sensor is mounted on the display device. Further, the visibility of the display device is reduced by a reduction in brightness of the display device resulting from the increase in the thickness of the display device.
On the other hand, the on-cell type touch sensor shares a glass substrate with the display device because the touch sensor has the structure in which the touch sensor is formed on the surface of the glass substrate of the display device. Therefore, a thickness of the display device using the on-cell type touch sensor is less than a thickness of the display device using the add-on type touch sensor. However, the entire thickness of the display device using the on-cell type touch sensor increases because of a touch driving electrode layer, a touch sensing electrode layer, and an insulating layer for insulating the touch driving electrode layer and the touch sensing electrode layer which constitute the on-cell type touch sensor. Further, the number of processes for manufacturing the display device using the on-cell type touch sensor increases, and thus the manufacturing cost increases.
Accordingly, the need for a touch sensor integrated type display device capable of solving the above-described problems has arisen. An example of the touch sensor integrated type display device includes Korean Patent Application No. 10-2013-0110906.
A touch sensor integrated type display device disclosed in Korean Patent Application Laid-Open No. 10-2013-0110906 divides display common electrodes and allows the display common electrodes to serve as touch sensing electrodes. Hence, the touch sensing electrodes are separately required. Thus, the touch sensor integrated type display device disclosed in Korean Patent Application Laid-Open No. 10-2013-0110906 can solve the problem generated in the add-on type touch sensor and the on-cell type touch sensor.
However, in the touch sensor integrated type display device disclosed in Korean Patent Application Laid-Open No. 10-2013-0110906, when there is a change (i.e., change in a display pattern depending on image information) in the screen in a display drive, an alignment state of liquid crystal is changed and thus a dielectric constant is changed. Hence, a capacitance between a touch driving electrode and the touch sensing electrode is changed. In particular, the change in the dielectric constant depending on the change in the alignment state of the liquid crystal at a boundary between the touch driving electrode and the touch sensing electrode greatly affects the change in the capacitance between the touch driving electrode and the touch sensing electrode. In this state, when a touch driving voltage is applied to the touch driving electrode, the touch sensing electrode recognizes the touch driving voltage as changes in the capacitance.
Accordingly, the touch sensor integrated type display device disclosed in Korean Patent Application Laid-Open No. 10-2013-0110906 erroneously recognizes the touch operation even when there is no touch operation, and thus generates the erroneous operation.